1. Field of the Invention
The invention concerns a device for positioning a part, more especially a slide or table of a machine tool or the like, the device having at least one stop.
2. Discussion of the Prior Art
In positioning devices of the kind initially referred to, it is known practice to provide stops having movable sensors which act on switches which in turn switch off the drive for moving the part when the switch is actuated by the sensor (see for example German Patent Specification No. 1,134,915). With this kind of stop there is no certainty as to how rapidly the movement will be halted after the stop has responded, i.e. the extent to which the part runs past the position preset by means of the stop is unknown.
Although, in the case of digitally controlled machines, it it also known to determine electrically a difference between the position reached and a required position, and to feed this difference to a control unit for the purpose of making a correction (German Patent Specification No. 1,577,485 as laid open), this type of stop can, however, only be used in conjunction with complicated and expensive digitally controlled machines.